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Baltimore crime analysts have been contaminating evidence with their own DNA - a revelation that led to the dismissal this week of the city Police Department's crime lab director and prompted questions yesterday from defense attorneys and forensic experts about the professionalism of the state's biggest and busiest crime lab.

Edgar Koch, who had been the city lab's director for the past decade, was fired Tuesday because of the DNA contamination and other "operational issues," said police spokesman Sterling Clifford.

He declined to elaborate on the other issues and said no one else was terminated.

City officials said the employee contamination did not lead to anyone being falsely accused of a crime, and they played down its importance.But Baltimore's top public defender called the findings "atrocious" and Baltimore State's Attorney Patricia C. Jessamy said she has asked her senior staff to review the potential impact on open and closed cases.

By introducing their own DNA into crime evidence, lab employees may have created more work for detectives and made prosecutions harder, as the presence of unknown DNA can leave the impression of a phantom suspect, experts said.

Defense attorneys said any flaws in the city's handling of DNA could raise broader questions about evidence that is generally considered infallible. As testing becomes more sophisticated and new standards for labs emerge, cities across the country, including Houston and Seattle, have been discovering contamination issues that in some cases led to convictions being overturned. [Mark Godsey]